The Temeraire Series by Naomi Novik

OK, so it's the Napoleonic wars, but what if instead of fighting them with just ships and cannons and muskets and stuff, they also used...dragons? If that pitch doesn't grab you, I don't know quite what to say to you. Novik has worked out in intricate and deeply plausible detail her vision of the dragons' biology and the sociology of their cooperation with humans, but what makes the series sing is her spot-on handling of the historical milieu and the characters who inhabit it. Think of Patrick O'Brian's Aubrey and Maturin books, with a sparkling dash of Jane Austen, and you'll just about have it. Then add dragons, and you'll get why Novik's books have been optioned by director Peter "Lord of the Rings" Jackson. (And when you're just about done, go back and read through Anne McCaffrey's ageless Dragonriders of Pern books.)